A bullet to the armoured temple is still going to be like getting getting in the head with a hammer. Pretty sure Hank (or Scale, both had their guns out) did that to render her unconscious since they aren’t cold blooded killers.
All the other shots missed but had the desired effect of panicking the mounts, and causing disarray and confusion in the rannite party. The ONLY shot that did hit, was one that rendered the biggest threat (hopefully) unconscious.

Yet, why would he let a gorgon live?
He should have seen, that she got knocked out…and even if he isn’t familiar with the powers of one, the others should have warned him…
She can turn the whole party inside out, in a matter of second, so PERMANENTLY putting her away would have been the safest thing to do.
I’m against killing in RL ~ but if i had to face a damn gorgon? I’d probably take no risk, if she could kill my friends with a single gaze…

Maybe they haven’t told him how dangerous she is yet. Also since they’re used to people knowing how dangerous a Gorgon is, maybe it hasn’t occurred to them that Hank doesn’t know about the Petrify gaze.

Also Hank being Hank would still have a problem shooting an *unarmed* woman, since him being a gentleman and all.